tracing/kprobe: Add kprobe_event= boot parameter

			Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,

			the default is off.

	kprobe_event=[probe-list]

			[FTRACE] Add kprobe events and enable at boot time.

			The probe-list is a semicolon delimited list of probe

			definitions. Each definition is same as kprobe_events

			interface, but the parameters are comma delimited.

			For example, to add a kprobe event on vfs_read with

			arg1 and arg2, add to the command line;

			      kprobe_event=p,vfs_read,$arg1,$arg2

			See also Documentation/trace/kprobetrace.rst "Kernel

			Boot Parameter" section.

	kpti=		[ARM64] Control page table isolation of user

			and kernel address spaces.

			Default: enabled on cores which need mitigation.

The first column is event name, the second is the number of probe hits,

the third is the number of probe miss-hits.

Kernel Boot Parameter

---------------------

You can add and enable new kprobe events when booting up the kernel by

"kprobe_event=" parameter. The parameter accepts a semicolon-delimited

kprobe events, which format is similar to the kprobe_events.

The difference is that the probe definition parameters are comma-delimited

instead of space. For example, adding myprobe event on do_sys_open like below

  p:myprobe do_sys_open dfd=%ax filename=%dx flags=%cx mode=+4($stack)

should be below for kernel boot parameter (just replace spaces with comma)

  p:myprobe,do_sys_open,dfd=%ax,filename=%dx,flags=%cx,mode=+4($stack)

Usage examples

--------------

#include <linux/rculist.h>

#include <linux/error-injection.h>

#include <asm/setup.h>  /* for COMMAND_LINE_SIZE */

#include "trace_dynevent.h"

#include "trace_kprobe_selftest.h"

#include "trace_probe.h"

#define KPROBE_EVENT_SYSTEM "kprobes"

#define KRETPROBE_MAXACTIVE_MAX 4096

#define MAX_KPROBE_CMDLINE_SIZE 1024

/* Kprobe early definition from command line */

static char kprobe_boot_events_buf[COMMAND_LINE_SIZE] __initdata;

static int __init set_kprobe_boot_events(char *str)

{

	strlcpy(kprobe_boot_events_buf, str, COMMAND_LINE_SIZE);

	return 0;

}

__setup("kprobe_event=", set_kprobe_boot_events);

static int trace_kprobe_create(int argc, const char **argv);

static int trace_kprobe_show(struct seq_file *m, struct dyn_event *ev);

}

#endif /* CONFIG_PERF_EVENTS */

static __init void enable_boot_kprobe_events(void)

{

	struct trace_array *tr = top_trace_array();

	struct trace_event_file *file;

	struct trace_kprobe *tk;

	struct dyn_event *pos;

	mutex_lock(&event_mutex);

	for_each_trace_kprobe(tk, pos) {

		list_for_each_entry(file, &tr->events, list)

			if (file->event_call == &tk->tp.call)

				trace_event_enable_disable(file, 1, 0);

	}

	mutex_unlock(&event_mutex);

}

static __init void setup_boot_kprobe_events(void)

{

	char *p, *cmd = kprobe_boot_events_buf;

	int ret;

	strreplace(kprobe_boot_events_buf, ',', ' ');

	while (cmd && *cmd != '\0') {

		p = strchr(cmd, ';');

		if (p)

			*p++ = '\0';

		ret = trace_run_command(cmd, create_or_delete_trace_kprobe);

		if (ret)

			pr_warn("Failed to add event(%d): %s\n", ret, cmd);

		cmd = p;

	}

	enable_boot_kprobe_events();

}

/* Make a tracefs interface for controlling probe points */

static __init int init_kprobe_trace(void)

{

	if (!entry)

		pr_warn("Could not create tracefs 'kprobe_profile' entry\n");

	setup_boot_kprobe_events();

	return 0;

}

fs_initcall(init_kprobe_trace);